Process for enhancing growth promotion in animals

ABSTRACT

There are provided novel furfuryl thiourea compounds which are effective for enhancing the growth rate of meat-producing animals and for improving the efficiency of feed utilization thereby, when administered to said animals in effective amounts in or with their feed or by parenteral administration.

The present invention relates to novel furfuryl thiourea compounds. More particularly, it relates to methods for preparing the same and furfuryl thiourea compounds having the structure: ##STR1## wherein R₁ is hydrogen, halogen, alkyl C₁ -C₄, alkoxy C₁ -C₄, CF₃, alkylthio C₁ -C₄, nitro, cyano, C₁ -C₄ alkanoyl, --COOR₄ or ##STR2## R₂ and R₃ are each selected from the group consisting of hydrogen, halogen, alkyl C₁ -C₄ and alkoxy C₁ -C₄ ; R₄ is hydrogen or alkyl C₁ -C₄ ; R₅, R₆ and R₇ are each hydrogen or alkyl C₁ -C₄, preferably methyl; with the proviso that when two of said R₁, R₂ and R₃, are hydrogen, the remaining R group cannot be hydrogen, chloro, methyl or methoxy. Still more particularly, the invention is concerned with a method for enhancing the growth rate of animals and improving the efficiency of feed utilization thereby, by orally or parenterally administering to said animals an effective amount of the furfuryl thiourea compound hereinabove identified.

It has been surprisingly found that meat animals' feed efficiency can be markedly improved by orally administering to said animals in or with the feed an amount of furfuryl thiourea compound equivalent to between 0.0001% to 1.00% (1-10,000 ppm). The preferred amount for poultry for instance is 0.0001% to 0.01% (1-100 ppm); for cattle and sheep for instance, the preferred amount is 0.0001% to 0.1% (1-1000 ppm); and for swine for example, the preferred amount is 0.0001% to 0.05% (1-500 ppm) by weight of feed.

In practice, the furfuryl thiourea compound is generally formulated as a premix and/or animal feed supplement which is admixed with a nutritionally balanced feed or added to the feed as a top dressing, or the like. Premixes may be blending about 70% to 95% by weight of an edible diluent such as soybean meal, ground corn, ground rice hulls, rice flour, or the like, with about 1% to 30% by weight of the active furfuryl thiourea compound.

The growth rate of animals is also improved when a furfuryl thiourea as defined above is administered as a subcutaneous implant under the skin of the animal. Implants are generally in the form of a paste or pellet which permits the active compound to be released into the bloodstream of the animal over an extended period of time, as for example, from several weeks to several months.

Whether the implant is in the form of a paste or a pettet is a matter of choice. Pettet-type implants which can be used in accordance with this invention may be prepared by admixing from about 50% to 95% by weight of a furfuryl thiourea compound with from about 50% to 5% by weight of a pharmaceutically acceptable carrier, such as Castorwax (i.e., glyceryl 12-hydroxysterate), beeswax, starch, or a high molecular weight (i.e., 4000) polyethylene glycol, or mixtures thereof, along or in combination with a small amount of a lubricant, such as zinc stearate or magnesium stearate. A small amount of polyvinylpyrrolidone and dibutylphthalate may also be incorporated in the above-defined formulations.

Paste implants can be prepared using the same percentages or drug as stated above, but employing a mixture of high molecular weight (i.e., 4000) polyethylene glycol and low molecular weight (i.e., 400) polyethylene glycol alone, or in combination with, Castorwax or beeswax and/or polyvinylpyrrolidone.

In general, implants can vary in size and weight, but usually range between 10 mg and 100 mg per implant. Advantageously, with this method of application, the drug can be administered at periodic intervals throughout the feeding period of the animals. Moreover, formulations and intervals between implantations can be varied to provide a daily drug release of generally about 0.0005 mg to 0.2 mg per kg of body weight, and preferably 0.001 mg to 0.1 mg per kg of body weight.

Typical implant formulations are as follows:

    ______________________________________                                         Typical Pellet Implant Formulations                                                                    Preferred                                              ______________________________________                                         (A)   1-Furfuryl-2-Thio-3-(2,6-xylyl urea                                                                    50.0%*                                                 Lubricant (i.e., magnesium stearate)                                                                   0.5%*                                                  Glyceryl 12-Hydroxystearate-QS                                           (B)   1-Furfuryl-3-mesityl-2-Thiourea                                                                        60.0%                                                  Polyethylene glycol 4000                                                                               10.0*                                                  Beeswax-QS                                                               (C)   1-(2,6-diethylphenyl)-3-furfuryl-2-                                            thiourea                30.0 mg                                                Beeswax                 1.0 mg                                                 Magnesium stearate      1.5 mg                                                 Dibutylphthalate        1.0 mg                                                 Polyvinylpyrrolidone (10% Solution)-QS                                   Typical Paste Implant Formulation                                                                      Preferred                                              ______________________________________                                         (A)   1-Furfuryl-3-(o-methoxyphenyl)-2-                                                                      200 mg                                                 thiourea                                                                       Polyethylene glycol 4000 (30% to 50%)                                                                  40%*                                                   Polyethylene glycol 400-QS                                               ______________________________________                                          *Percent by weight                                                       

In accordance with this invention, a furfuryl thiourea compound having the structure: ##STR3## wherein R₁ is hydrogen, halogen, alkyl C₁ -C₄, alkoxy C₁ -C₄, CF₃, alkylthio C₁ -C₄, nitro, cyano, C₁ -C₄ alkanyol, --COOR₄ or ##STR4## R₂ and R₃ each represent members selected from hydrogen, halogen alkyl C₁ -C₄ and alkoxy C₁ -C₄ ; R₄ is hydrogen or alkyl C₁ -C₄ ; and R₇ is hydrogen or alkyl C₁ -C₄ ; can be prepared by reacting furfurylisothiocyanate: ##STR5## with an equivalent amount of an appropriately substituted aniline having the structure: ##STR6## where R₁, R₂, R₃ and R₇ are as defined hereinabove, in the presence of an inert organic solvent such as an aromatic hydrocarbon, aliphatic hydrocarbon, chlorinated hydrocarbon, tetrahydrofuran, dioxane, or the like, at a temperature between about 20° and 100° C. Inert solvents, such as hexane, heptane, pentane, benzene, toluene, chloroform, tetrahydrofuran (THF), xylene and the like are illustrative of those which may be employed in this reaction.

The furfurylisothiocyanate intermediate herein can be prepared by reacting furfurylamine with carbon disulfide in the presence of base and treating the thus formed reaction mixture with sodium hypochlorite. This reaction is preferably conducted in the presence of an inert solvent such as methylene chloride at a temperature between about 0° and 10° C.

These reactions may be illustrated as follows: ##STR7## wherein R₁, R₂, R₃ and R₇ are as defined above.

The furfuryl thiourea compounds of the present invention may also be prepared by reacting the appropriately substituted phenylisothiocyanate with an equivalent amount of an appropriately substituted furfurylamine. The reaction is preferably conducted in an inert solvent such as hexane, benzene, toluene, or the like, at a temperature between about 20° and 60° C. The reaction may be illustrated as follows: ##STR8## where R₁, R₂, R₃, R₅ and R₆ are as described above.

A still further embodiment for the preparation of the furfuryl thiourea compounds of the present invention involves the preparation of ammonium furfuryldithiocarbamate by reaction of furfurylamine with carbon disulfide in the presence of aqueous ammonium hydroxide. The furfuryldithiocarbamate is then converted to furfurylisothiocyanate by reaction with aqueous sodium hypochlorite. The thus-prepared furfurylisothiocyanate may then be reacted, as described above, with the appropriate aniline to yield the desired furfuryl thiourea.

The following examples serve to further illustrate the present invention.

EXAMPLE 1 Preparation of 1-Furfuryl-2-thio-3-(2,6-xylyl)urea

A solution of 125.4 g of 2,6-dimethylphenyl isothiocyanate is added dropwise to a mixture of 74.6 g of furfurylamine in 1.5 liters of hexane. The mixture is stirred at room temperature for 16 hours. The solid product is collected by filtration and dried to afford 107.8 g of the title compound, m.p. 102°-105°.

The above procedure is repeated in every detail except that the appropriately substituted phenylisothiocyanate is substituted for 2,6-dimethylphenylisothiocyanate to yield the compounds described below:

    ______________________________________                                                                 Melting Point                                          Compound                ° C.                                            ______________________________________                                         1-(2,6-dichlorophenyl)-3-furfuryl-2-                                                                   163-167                                                thiourea                                                                       1-furfuryl-2-thio-3-(2,3-xylyl)urea                                                                    102-104                                                1-furfuryl-3-(o-nitrophenyl)-2-thiourea                                                                85-89                                                  1-(2,6-diisopropylphenyl)-3-furfuryl-2-                                                                130-134                                                thiourea                                                                       1-furfuryl-3-[o-(methylthio)phenyl]-2-                                                                 99-102                                                 thiourea                                                                       1-furfuryl-3-mesityl-2-thiourea                                                                        127-131                                                1-(2,6-diethylphenyl)-3-furfuryl-2-                                                                    84-85                                                  thiourea                                                                       1-furfuryl-2-thio-3-o-tolylurea                                                                        86-89                                                  1-furfuryl-2-thio-3-(α,α,α-trifluoro-o-                                              103-107                                                tolylurea                                                                      1-(o-fluorophenyl)-3-furfuryl-2-thiourea                                                               109-113                                                1-furfuryl-3-(o-methoxyphenyl)-2-thiourea                                                              108-111                                                1-furfuryl-2-thio-3-[o-(p-tolylthio)-                                                                  80-83                                                  phenyl]urea                                                                    1-furfuryl-3-(p-nitrophenyl)-2-thiourea                                                                114-117                                                1-furfuryl-2-thio-3-(2,4-xylyl)urea                                                                    120-123                                                1-(p-Cyanophenyl)-3-furfuryl-2-thiourea                                                                156-159                                                1-(p-chlorophenyl)-3-furfuryl-2-thiourea                                                               116-119                                                1-furfuryl-2-thio-3-(2,6-xylyl)urea                                                                    125-138                                                1-(p-acetylphenyl)-3-furfuryl-2-thiourea                                                               147-149                                                1-furfuryl-2-thio-3-p-tolylurea                                                                        166-169                                                1-(o-cyanophenyl)-3-furfuryl-2-thiourea                                                                169-172                                                1-furfuryl-3-(p-methoxyphenyl)-2-thiourea                                                              110-114                                                3-(2,6-dichlorophenyl)-1-furfuryl-1-                                                                   133-137                                                methyl-2-thiourea                                                              1-(2-ethyl-p-tolyl)-3-furfuryl-2-thiourea                                                              79-72                                                  1-furfuryl-1-methyl-2-thio-3-(2,6-xylyl)-                                                              130-133                                                urea                                                                           1-(α-methylfurfuryl)-2-thio-3-(2,6-                                                              138-141                                                xylyl)urea                                                                     ______________________________________                                    

EXAMPLE 2 Preparation of 1-Furfuryl-2-thio-3-(2,6-xylyl)urea

Furfurylamine (9.71 g) is added over 30 minutes to a stirred, cooled mixture of 8.84 g of NaOH, 20 ml of CH₂ Cl₂, 15 ml of H₂ O and 7.5 ml of CS₂. The mixture is stirred 55 minutes in the ice bath and 600 ml of 5.25% aqueous NaOCl solution is added over 1 hour and 45 minutes (temperature is maintained at 8° C. or less). After stirring 16 hours at 20° C., the reaction mixture is extracted three times with CH₂ Cl₂ (total volume of combined CH₂ Cl₂ extracts is 600 ml). The CH₂ Cl₂ extract is washed with 2×100 ml of H₂ O, dried with Na₂ SO₄ and evaporated to give 12.4 g of crude furfurylisothiocyanate.

The crude isothiocyanate is shaken with hexane (2×60 ml) and the hexane-soluble material is added over 10 minutes to a stirred solution of 12.1 g of 2,6-dimethylaniline in hexane (50 ml). After sixteen hours, the white solid is collected, washed with 3×10 ml hexane and air dried to give 10.03 g (38.5% yield) of the desired thiourea having a melting point equal to 103°-106° C.

Employing the appropriately substituted aniline in the above-reaction in place of 2,6-dimethylaniline there is obtained 3-furfuryl-1-methyl-2-thio-1-(2,6-xylyl)urea having a melting point equal to 47.5°-49.5° C.

EXAMPLE 3 Preparation of Ammonium furfuryldithiocarbamate

Furfurylamine (4.85 g) is added dropwise over 50 minutes to a vigorously stirred mixture of 3.75 ml of CS₂ and 8.3 ml of 29.7% aqueous ammonia cooled in ice and methyl alcohol. The cooling bath is removed and the thick orange suspension stirred 16 hours more, filtered and air dried to yield 3.11 g (32.7% yield) of desired product characterized by m.p. equal to 88° C. dec.

EXAMPLE 4 Preparation of 1-Furfuryl-2-thio-3-(2,6-xylyl)urea

A 5.25% aqueous NaOCl solution (60 ml) is added to a stirred, cooled suspension of 1.9 g of ammonium furfuryldithiocarbamate in 20 ml of CH₂ Cl₂ at such a rate that the temperature does not exceed 6° C. The mixture is stirred one hour at 20° C. and extracted with 3×50 ml of CH₂ Cl₂. The combined extracts are washed with H₂ O (2×50 ml) dried (Na₂ SO₂) and evaporated to afford 1.13 g of (81.2% yield) of crude furfurylisothiocyanate (NMR, IR are supportive of the structure).

The crude isothiocyanate is treated with 6 ml of hexane and the hexane soluble material is added to a stirred solution of 0.98 g of 2,6-dimethylaniline in 5 ml of hexane. After sixteen hours the solid is collected, washed with 2×3 ml of hexane and air dried to give 1.27 g (60% yield) of 1-furfuryl-2-thio-3-(2,6-xylyl)urea.

EXAMPLE 5 Evaluation of Test Compounds for Enhancing the Growth Rate and Improving Feed Efficiency in Sheep

To determine the effectiveness of 1-furfuryl-2-thio-3-(2,6-xylyl)urea for increasing the growth rate and improving feed efficiency in sheep, wether lambs are randomly allocated to pens, five lambs per pen. Six pens per treatment are used. All animals are placed in their pens and held overnight without water. The following morning all lambs are weight, returned to their pens and provided with test diet offered ad libitum. Water is also offered ad libitum. At two-week intervals water is withheld from all lambs overnight. The folowing morning all lambs are weighed. During the entire test period unconsumed feed is collected and weighed back prior to the morning feeding and saved. The collected refused feed is weighed every two weeks on the day the lambs are weighed.

Six weeks after testing is initiated the trials are terminated and the lambs weighed. The average daily gain and the amount of feed consumed per unit of gain are then determined for each treatment group. Data obtained are reported in table I below.

    ______________________________________                                         Diet                                                                                              % by                                                        Ingredient         weight                                                      ______________________________________                                         Soybean Oil Meal   13                                                           (49%)                                                                         Ground Yellow Corn 30                                                          Ground Corn Cobs   30                                                          Dehydrated Alfalfa 15                                                           Meal                                                                          Molasses           10                                                          Iodized Salt       0.5                                                         Dicalcium Phosphate                                                                               1.0                                                         Pre-mix            0.5                                                           Total            100                                                         Pre-mix for One Ton of Feed                                                                       (grams)                                                     ______________________________________                                         Trace Minerals     454                                                         Vitamin A (30,000 Iu/g)                                                                           133                                                         Vitamin D3 (200,000 Iu/g)                                                                         5                                                           Vitamin E (125,000 Iu/g)                                                                          49.5                                                        Corn Oil           100                                                         Ground Corn        3798.5                                                      ______________________________________                                    

                  TABLE I                                                          ______________________________________                                         Weight Gain and Feed Efficiency of Control and                                 1-Furfuryl-2-Thio-3-(2,6-xylyl)urea-Treated Wether Lambs                       Six Week Data                                                                                                          %                                                                              Improve-                                          ppm                          ment                                              in     ADG      % Over Feed/ Over                                   Treatment  diet   (grams)  Control                                                                               Gain  Control                                ______________________________________                                         Control    0      204      --     9.73  --                                     1-Furfuryl-2-Thio                                                                         25     212       + 3.9 9.00  + 7.5                                  3-(2,6-xylyl)urea                                                              "          50     234      + 14.7 8.76  + 10.0                                 "          100    236      + 15.7 8.80  + 9.6                                  ______________________________________                                          ADG = Average daily gain                                                 

EXAMPLE 6 Evaluation of Test Compounds as Animal Feed Additives for the Enhancement of the Growth Rate of Poultry Test Animals

One day old Hubbard X Hubbard Crossbred Chicks, randomly allotted to pens of ten chicks (5 males and 5 females) each.

Procedure

Eight pens of chicks are used for unmedicated controls, and four pens of chicks are used it each level of drug. The duration of the experiment is 13 days.

The controls are offered an unmedicated diet of Broiler ration No. 453 (composition given below) and water ad libitum. Medicated chicks are offered the same diet containing the test drug at the levels indicated above, and water ad libitum. The weight of the chicks is determined at the beginning and on completion of the experiments. Weight gains and the amount of feed consumed are also determined. The thus obtained data are averaged and summarized in Table II below, wherein the percent improvement in weight gains and feed/gain ratios are given.

                                      TABLE II                                     __________________________________________________________________________     Effects of Test Compounds on Weight Gain and Feed Efficiency                   of Chicks in Thirteen Day Battery Tests                                                                                   % improvement                                   Dosage                                                                             Weight/chick(g)                                                                         Weight gain                                                                           Feed Consumed                                                                             over controls                       Treatment   ppm start                                                                              finish                                                                              per chick(g)                                                                          per chick(g)                                                                           F/G                                                                               gain                                                                               F/G                             __________________________________________________________________________     Control   0     44.6                                                                               314.1                                                                               269.5  377.3   1.40                                                                              --  --                              1-(6-ethyl-o-tolyl)-3-                                                                   2.5   44.6                                                                               316.8                                                                               272.2  375.6   1.38                                                                              + 1.0                                                                              + 1.4                           furfuryl-2-thiourea                                                            1-furfuryl-3-phenyl-                                                                     2.5   44.6                                                                               317.9                                                                               273.3  379.9   1.39                                                                              + 1.4                                                                              + 0.8                           thiourea                                                                       Control   0     44.6                                                                               306.7                                                                               262.1  369.6   1.41                                                                              --  --                              1-furfuryl-2-thio-3-                                                                     2.5   44.6                                                                               315.1                                                                               270.5  373.3   1.38                                                                              + 3.2                                                                              + 2.0                           (2,6-xylyl)urea                                                                1-furfuryl-3-mesityl-                                                                    2.5   44.6                                                                               317.1                                                                               272.5  378.8   1.39                                                                              + 3.9                                                                              + 1.9                           2-thiourea                                                                     1-(2,6-diethylphenyl)-                                                                   2.5   44.6                                                                               314.9                                                                               270.3  375.7   1.39                                                                              + 3.1                                                                              + 1.9                           3-furfuryl-2-thiourea                                                          1-furfuryl-2-thio-3-                                                                     2.5   44.6                                                                               311.7                                                                               267.1  373.9   1.40                                                                              + 1.9                                                                              + 1.2                           o-tolylurea                                                                    Control   0     38  263.8                                                                               225.8  338.7   1.51                                                                              --  --                              1-(2,6-dichlorophenyl)-                                                                  2.5   38  267.2                                                                               229.2  343.3   1.51                                                                              + 1.5                                                                              --                              3-furfuryl-2-thiourea                                                          1-furfuryl-3-(o-nitro-                                                                   2.5   38  273.3                                                                               235.3  349.4   1.49                                                                              + 4.2                                                                              + 1.0                           phenyl)-2-thiourea                                                             1-furfuryl-3-(o-methoxy-                                                                 2.5   38  271.4                                                                               233.4  344.4   1.48                                                                              + 3.4                                                                              + 1.9                           phenyl)-2-thiourea                                                             1-furfuryl-3-(p-nitro-                                                                   2.5   38  267.3                                                                               229.3  340.1   1.49                                                                              + 1.6                                                                              + 1.0                           phenyl)-2-thiourea                                                             __________________________________________________________________________

EXAMPLE 7 Evaluation of Test Compounds for Enhancing the Growth Rate and Improving Feed Efficiency in Swine

In the following test female and castrate weanling pigs are allocated to pens, 5 pigs per pen (3 male, 2 female) per treatment. These pigs are weighed on the day the test is initiated and then they are placed in their pens. A sufficient amount of feed to last one week is added to each feeder at the start of the test and each week thereafter. Both water and feed are provided ad libitum and all pigs are weighed every other week after the trial is begun. The trial is continued for 42 days after which the pigs are weighed and the test terminated. The amount to feed consumed per pen is recorded every two weeks on the day the pigs are weighed. Data obtained are reported in table III below.

    ______________________________________                                         Swine Grower Diet                                                              Ingredient        %                                                            ______________________________________                                         Corn Ground       77.825                                                       Soybean Meal      17.50                                                        Meat + Bone Meal  2.50                                                         Di Calcium Phosphate                                                                             0.75                                                         Iodized Salt      0.50                                                         Limestone         0.60                                                         Vitamin Premix    0.25                                                         Mineral Premix    0.075                                                                          100.000                                                      ______________________________________                                    

                  TABLE III                                                        ______________________________________                                         Effects of 1-Furfuryl-2-thio-3-(2,6-xylyl)urea on Weight Gain                  and Feed Efficiency of Weanling Pigs;                                          A six week study                                                                                   ADG      %          %                                      Treatment   ppm     (Grams)  Control                                                                              F/G  Control                                ______________________________________                                         Control     0       779      --    2.87 --                                     1-Furfuryl-2-thio-3-                                                                       10      826      +6.0  2.73 +4.9                                   (2,6-xylyl)urea                                                                            50      765      -1.8  2.77 +3.5                                               100     810      +4.0  2.79 +2.8                                   ______________________________________                                     

We claim:
 1. A method for enhancing the growth rate of an animal and increasing the efficiency of feed utilization thereby, comprising: orally or parenterally administering to said animal an effective amount of a compound having the structure: ##STR9## wherein R₁ is hydrogen, halogen, alkyl C₁ -C₄, alkoxy C₁ -C₄, CF₃, alkylthio C₁ -C₄, nitro, cyano, C₁ -C₄ alkanoyl --COOR₄ or ##STR10## R₂ and R₃ each represent hydrogen, halogen, alkyl C₁ -C₄ or alkoxy C₁ -C₄ ; R₄ is hydrogen or alkyl C₁ -C₄ ; R₅, R₆ and R₇ are each hydrogen or alkyl C₁ -C₄.
 2. The method according to claim 1 wherein R₁ is alkyl C₁ -C₄ ; R₂ and R₃ are each hydrogen or alkyl C₁ -C₄ ; R₅, R₆ and R₇ are each hydrogen.
 3. The method according to claim 1 wherein said compound is administered to said animals in an amount equivalent to between 1 and 10,000 ppm in or with an animal feed.
 4. The method according to claim 1 wherein said animals are sheep, cattle, swine, goats or poultry.
 5. The method according to claim 1 wherein said compound is 1-furfuryl-2-thio-3-(2,3-xylyl)urea.
 6. The method according to claim 1 wherein said compound is 1-furfuryl-2-thio-3-(2,6-xylyl)urea.
 7. The method according to claim 1 wherein said compound is 1-furfuryl-3-mesityl-2-thiourea.
 8. The method according to claim 1 wherein said compound is 1-(2,6-dichlorophenyl)-3-furfuryl-2-thiourea.
 9. The method according to claim 1 wherein said compound is 1-(p-acetylphenyl)-3-furfurty-2-thiourea.
 10. An animal feed composition comprising: an edible animal feedstuff containing from 0.0001% to 1.0% by weight of a compound having the formula: ##STR11## wherein R₁ is hydrogen, halogen, alkyl C₁ -C₄, alkoxy C₁ -C₄, CF₃, alkylthio C₁ -C₄, nitro, cyano, C₁ -C₄ alkanoyl, --COOR₄ or ##STR12## R₂ and R₃ are each hydrogen, halogen, alkyl C₁ -C₄ or alkoxy C₁ -C₄ ; R₄ is hydrogen or alkyl C₁ -C₄ ; R₅, R₆ and R₇ each represent hydrogen or alkyl C₁ -C₄. 